Recently, there is a growing demand on biojet fuel in an effort to reduce greenhouse gas production. Among various technologies for manufacturing biojet fuel, those which use bioethanol as a raw material have an advantage in that they enable securing a large amount of relatively cheap raw materials.
Jet fuel is required to have a challenging property such as high energy density without being frozen at high altitudes, and in this regard, it is preferred that jet fuel have a distribution of a C4-10 composition to secure the above property.
Accordingly, in the technologies for manufacturing jet fuel using bioethanol, the technology of converting the ethylene (C2), which was prepared by ethanol dehydration, into C8-16 oligomers is absolutely necessary. The C8-16 oligomers prepared as such can be subjected to subsequent hydrogenation and distillation processes, and finally jet-grade fuel can be obtained therefrom.
However, those technologies which convert ethylene into C8-16 oligomers by a one-step catalytic reaction have a problem in that they not only have low selectivity to oligomers of C8-16 or higher but also oligomers of C10 or higher attach to the surface of the catalyst because oligomers of C10 or higher are produced at high temperature and thus the catalyst is easily deactivated (Vasile Hulea et al., Journal of Catalysis 225 (2004), 213-222).
Under the circumstances, the present inventors have made efforts to solve the above problems, and as a result, they have discovered that a total of two-step ethylene oligomerization can not only increase the selectivity to oligomers of C10 or higher but also prevent the deactivation of the catalyst involved therein, thereby completing the present invention.